The chemistry of block copolymers is extensive and well developed. They can be used to combine the properties of different polymers in one material. For example, a polymer having hydrophilic properties can form one block and a polymer having hydrophobic properties can form another block. Thus, one material can have combinations of properties that neither constituent polymer possesses alone. This can be of significant utility in the medical device arena.
Polymers used to create medical devices are typically chosen for their bulk properties; however, it is often desirable for the surfaces of such medical devices to possess different properties than that of the bulk polymer. For example, it may be desirable for a polymer surface to have a different level of compatibility with other polymers or tissues, surface energy, etc., than that of the bulk polymer. Thus, block copolymers are desirable materials to investigate for their utility in modifying polymer surfaces for medical device applications.
Block copolymers have been used to modify polyurethane surfaces, which are important biomedical polymers used in implantable devices such as artificial hearts, cardiovascular catheters, pacemaker lead insulation, etc. Such block copolymers have been used to enhance antimicrobial properties, lubricity, barrier properties, anticoagulant properties, and the like. For example, U.S. Pat. No. 4,675,361 (Ward, Jr.) discloses a block copolymer for improved biocompatibility. Also, U.S. Pat. No. 5,302,385 (Khan et al.) discloses a polyurethane-poly(vinyl pyrrolidone) copolymer foam having antimicrobial properties coated on a catheter. The resultant polymer is highly branched or a network polymer without a well-defined or controllable block architecture.
Other block copolymers are needed for modifying the surface properties of medical devices.